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Blood Typing Facts and Statistics
Q: What does forward blood typing mean?
Q:
What does the above mean for transfusions?
Q:
Statistically, What is the Blood Type Frequency percentage?
Q: What about the statistical percentage of Blood
Type and Rh factor?
Q: If
both parents blood type is known, what are the possible blood types of their
children?
Q: How does Rh factor affect
the giving of blood transfusions?
Q. Why is blood typing
important?
Q. What is alloimunization?
Q. What is a rare blood type?
Q. What is the universal donor?
Q. Why do
so many people who have had routine medical care not know their blood type?
Q: What does forward blood typing mean?
A:
In forward typing a sample of the blood is mixed
with serum that contains antibodies against type A blood ("anti-A serum").
Another sample of blood is then mixed with serum that contains antibodies
against type B blood ("anti-B serum"). Finally another blood sample is
mixed with serum that contains antibodies against type Rh Positive Blood
("anti-Rh serum). Patterns of clotting are then observed and
recorded as follows:
Type A blood clots when mixed with anti-A serum.
Type B blood clots when mixed with anti-B serum.
Type AB blood clots when mixed with both anti-A and anti-B serums.
Type O blood does not clot when mixed with either anti-A or anti-B serum.
Rh-positive blood clots when mixed with anti-Rh serum.
Rh-negative blood does not clot when mixed with anti-Rh serum |
Q:
What does the above mean for transfusions?
A:
Persons with type A blood can receive blood transfusions from donors with type A
or type O blood.
Persons with type B blood can receive transfusions from donors with type B or
type O blood.
Persons with type AB blood can receive transfusions from donors with type AB,
type A, type B, or type O blood.
Q:
Statistically, What is the Blood Type Frequency percentage?
A:
Blood Type frequency in percentage of total population:
Blood
Type |
%
Frequency |
O |
46% |
A |
40% |
B |
10% |
AB |
4% |
Q: What about the statistical percentage of Blood
Type and Rh factor?
A:
The overall statistical distribution of blood type plus Rh factor in the total
population is as follows:
Blood Type
|
Abbr
|
% Frequency
|
O Rh-positive
|
O+
|
38%
|
O Rh-negative
|
O-
|
7%
|
A Rh-positive
|
A+
|
34%
|
A Rh-negative
|
A-
|
6%
|
B Rh-positive
|
B+
|
9%
|
B Rh-negative
|
B-
|
2%
|
AB Rh-positive
|
AB+
|
3%
|
AB Rh-negative
|
AB-
|
1%
|
Note: Percentage
distribution may be different within specific racial and ethnic subgroup
Q: If both parents blood type is known, what are the possible blood types of
their children?
A: Blood type is determined
by the "alleles" that are inherited
from the parents. Alleles are possible types of a
particular gene, in this case the blood type gene. There are three basic blood
type alleles: A, B, and O. Children have two alleles,
one inherited from each parent. The possible combinations of the three alleles
are OO, AO,
BO, AB, AA,
and BB.
Blood types A and B are called co-dominant alleles,
while O is recessive. A co-dominant allele is apparent
even if only one is present; a recessive allele is apparent only if two
recessive alleles are present. Since blood type O is recessive, it is not
apparent if the person inherits an A or B allele along with it.
Therefore, the possible allele combinations result in a particular blood
type in this way:
Allele
Combination |
Results in |
Blood Type |
OO |
= |
O |
AO |
= |
A |
BO |
= |
B |
AB |
= |
AB |
AA |
= |
A |
BB |
= |
B |
Consequently, a
person with blood type B may have a B and an O allele, or they may have two B
alleles. If both parents are blood type B and both have a B and a recessive O,
then their children will either be BB (if each parent passed on the B allele),
BO (if one parent passed on B and the other parent passed on O), or OO (if both
parents passed on the O allele). If the child is BB or BO, they have blood type
B. If the child is OO, they will have blood type O.
When these basic blood type genetics
are understood, then it becomes relatively easy to
understand that it is not at all unusual for two parents with blood type
B (or blood type A) to have children with blood type O.
Parents'
Blood Types |
Possible
Children |
Impossible
Children |
A & A |
A, O |
B, AB |
A & B |
A, B, AB,O |
none |
A & AB |
A, B, AB |
O |
A & O |
A, O |
B, AB |
B & B |
B, O |
A, AB |
B & AB |
A, B, AB |
O |
B & O |
B, O |
A, AB |
AB & AB |
A, B, AB |
O |
AB & O |
A, B |
AB, O |
O & O |
O |
A, B, AB |
Similar to A,B,O and AB blood types, Rhesus
Factor (Rh +/-) genetics is determined from the possible allele combinations
inherited from each parent. The DNA of each parent carries two Rh alleles either
positive (+) or negative (-). The positive Rh factor allele is dominant over the
negative Rh factor allele meaning that if a parent's pair of Rh factor alleles
are one positive (+) and one negative (-), the positive allele will dominate the
negative allele and result in a positive Rh factor (Rh+). Therefore it is quite
possible that two parents with Rh+ factors to produce an Rh- child. Possible
combinations are shown below:
Parent 1
Rh Type |
Parent 2
Rh Type |
Impossible
Children |
Possible
Children |
+/+ |
+/+ |
+/- , -/- |
+/+ |
+/+ |
-/- |
+/+ , -/- |
+/- |
+/- |
+/+ |
-/- |
+/+ , +/- |
+/- |
+/- |
none |
+/+, +/-, -/- |
+/- |
-/- |
+/+ |
+/-, -/- |
-/- |
+/- |
+/+ |
+/-, -/- |
-/- |
-/- |
+/+, +/- |
-/- |
In the highlighted cells both the parents are Rh+ but carry a recessive Rh- allele. Statistically they
will produce an Rh- child 25% of the time.
Q: How does Rh factor affect
the giving of blood transfusions?
A:
Persons with Rh-positive blood can receive transfusions from donors with
Rh-positive and Rh-negative blood.
Persons with Rh-negative blood can only receive transfusions from donors with
Rh-negative blood.
Q. Why is blood typing
important?
A. When the body is exposed to something foreign, like a blood
transfusion, our immune system kicks in to protect us. One weapon the body
deploys is the production of antibodies, protein molecules released by plasma
cells that bind to a specific antigen. The antibodies couple with the antigens
on the surface of the invading cells and try to destroy the cells. A cross-match
is performed between the donor's blood and patient's blood to prevent this kind of reaction, which can range from
mild to very serious. Antigens are also found on white cells and platelets.
Additional testing, such as HLA testing or filtering may be performed in the
case of white cell or platelet transfusion.
Q. What is alloimunization?
A. Most people, on average, will only need blood one time in their lives, to help fight a
disease, restore blood lost during surgery or because of traumatic injury. But some patients, like sickle cell patients,
may need blood many times during their lives. If the blood they receive is not a
very close match, they will begin to reject transfusions, and an important
source of help and hope will be gone. To prevent that, blood for these patients
should be closely matched. Often, this will be a rare blood type. For sickle
cell patients, the best match will come from donors of African descent. Fully
one third of requests for rare blood received by the Red Cross is for a blood
type found exclusively among African Americans.
Q. What is a rare blood type?
A. Some patients require rare blood types found in only one in 1,000
donors, or even less frequently. Through the American Rare Blood Donor Registry
donors can be identified who have these rare blood types. When a need for their
special blood type arises, the blood bank can call upon this donor to give blood. The Red Cross also
freezes some rare units of red cells to assure their availability in a time of
need.
Q. What is the universal donor?
A. Type O negative donors are known as universal donors because their blood may be
transfused to patients of any other blood type in an emergency situation or if
the specific needed blood type is unavailable. Because any patient can receive O negative
blood, there is a constant need for O negative donors to give more often and shortages of
type O blood can have critical consequences in national disasters. Whatever a
person's blood type, they can be very important to someone in emergency crisis.
Q. Why do so many people
(estimated at 70% of the population),
who have had routine medical care not know their blood type?
A. Because they don't ask. Also there is the notorious reluctance among
medical professionals to inform patients of their chart details.

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